HID (High Intensity Discharge: Xenon bulbs are included in this technology)This technology replaced many applications using Halogen bulbs by virtue of lower power consumption for the same amount of lumens. The technology uses a ballast to build up a high intensity charge to transmit the power. 4200-6500°K color temp. (HMI is a similar technology that is higher CRI(over 90) but minimum bulbs are 120-200W at 24V with instant restrike ability, but slow to full power (2mins) and large size)Advantages: Long bulb life (500-1000 hours), high lumens/watt, lower power consumption (longer burn times) requiring smaller batteries.Disadvantages: Requires time to hit full power, no instant restrike (must be allowed to cool after being switched off),expensive bulb replacement ($100-300), lower CRI (60-75), bulky lamphead, not dimmable

LED (Light Emitting Diodes)The latest technology that has been around for awhile (think of your keychain and car key lights). Only recently used in underwater video lights. Color Temp 5500-7000°KAdvantages: High efficiency (lumens per watts), long life, very low power consumption, small size, instant on/off, variable power (dimmable).Disadvantages: CRI 62-96, expensive. heat sensitive. SPD is spikey compared to Tungsten/Halogen, which can cause issues with some camera sensors. Manufacturers tend to advertise peak lumens vs average, which can be as much as 30% less than peak output.

As noted in those discussions, each of these technologies have different aspects you will need to understand and decide if you want more of one or the other.

These aspects include:

Color Temperature:Measured in degrees Kelvin(°K) , light color temperature of the beam affects how we see the illuminated subject. Halogen lights are usually 3200°K which means they look a bit yellowish or "warmer". But Halogen also has 100CRI which means it is the most accurate of lighting sources for the color chart. HID/HMI/LED usually are in the 5000 to 9000°K range, which is more blusih or "colder". However with colored diffusers, the light color can be changed to match the look needed.

CRI : Color Rending IndexCRI is used to show how well light from whatever source renders a chart of 8 colors accurately. Tungsten/Halogens usually have 100% but if voltage falls, the CRI may also drop. HIDs tend to be in the 60-70 region, thus some colors are not represented correctly at the bulbs particular color temperature. Some LED and HMI usually have 90+ rating on the CRI. * CRI standard is used still today even though the standard is old. Critics say that the standard is old and biased toward continuous spectral distributions, thus against LED, HID and fluorescent systems which have irregular (spikey) spectral characteristics. A new proposed standard called Color Quality Scale (CQS) is being designed to correct and enhance the CRI standard.**CRI is also color temperature specific. It should be noted the CRI of each color temperature (eg. 100CRI at 3600°K and 70 CRI at 6500°K) cannot be compared to each other. That is, the 3600K light source's 100CRI can only be compared to another light source at of the same color temperature to be accurate. Direct comparison of CRI between light sources of 2 different color temperatures isn't accurate, but using them as a reference point at the desired color temperature, eg 4700K, it is comparable.

Alan Roberts, formerly of the BBC, introduced the EBU Television Lighting Consistency Index (TLIC), which evaluates testing of light source in software form. This includes testing of LEDs and showing any color shifts between different lights and the accuracy.

Lumens/watt:Lumens is the amount of light measured in foot candles. Lumens/watt is the ratio of how many lumens a light source can give out per watt of electricity. Obviously the higher the number the better. But note that the higher the wattage, the faster the battery drains. HID/LED traditionally have higher lumens/watt. The problem is that manufacturers of the lights tend to quote their OEM specification which usually is done in optimal conditions. Usually the actual output is lower, sometimes much lower. Another problem is that the methodology used is often not the same

Beam spread:All video lights are channelled through a reflector. The quality of the light is dependent on how the reflector spreads the light on the subject. A wider beam is better due to uniformity and the lack of hotspots. Use of diffusers help remove hotspots but absorb some of the light obviously. 60 to 180° reflectors are available. LED lights are a bunch of diodes in mini-reflectors thrown together whereas halogen and HID rely on reflectors and diffusers for an even beam. Generally for video the wider the beam the better, but obviously the wider beam doesn't seem as bright as a narrow beam which can cause hotspotting. The traditional round beam also is inefficient as a lot of light is lost since cameras shoot at 16:9 or 4:3 ratio.On the other hand, a wide beam will illuminate all the particles in the camera view, which isn't optimal for the best image. Still with ViDSLR cameras being able to use 180° fisheye lenses, a wide beam is becoming more useful than the narrower beam designs before the ViDSLR phenomenon, where FOV was limited to 100° in most cases.With big animals, a narrower beam is more useful as you only want to illuminate the animal and not the particulates.

There are other factors like restart time, strike time, bulb replacement, fragility of bulbs and even availability of bulbs as factors and of course, cost!

Battery Packs

Nickel Metal HydrideThe most common battery pack cell right now is NiMH. Most of these are now memory free and efficient, with long life. The disadvantages of NiMH are they need proper charging and reconditioning to maintain a healthy life, and also are average for watt/size. Most cells can take 500-1000 charges.

Lithium Polymer/IonThe new lithium packs come in the form of Li-Polymer battery packs. Found mostly in cellphones and laptop batteries, these batteries pack very small and have a nice watt/size ratio. The downside is they tend to age quickly regardless of charge, on average of 10-20% a year from date of manufacturing. They are also more expensive and have been known to explode in high temperatures (laptop battery recalls). There is also a shelflife limit.Note for US travellers: DOT rules that any large Li-Ion battery containing between 100-300Wh (8-25g Equivalent Lithium Content) must be installed in the device to be allowed in checked bags. No Li-Ion spares of similar Wh are allowed to be checked but up to 2 in cabin luggage are allowed.100Wh is approx 8.33AH at 12v. Whether this is enforced is another matter altogether.

Lithium Manganese (LiMn2The newest battery cells are now the Lithium Manganese batteries, which don't have the explosive reaction that Lithium Ion/Polymer battery cells have when punctured and thus safer for use underwater and also more robust. The capacity and charge density isn't as good as Li-Ion.

Lithium Iron Phosphate (LiFePo4)Due to airline restrictions on Li-Po/Li-Ion, the battery industry has come up with another alternative, LiFePO4 Lithium Iron Phosphate. This battery has about 86% of LiIon/LiPo batteries and like LiMg is not as combustive. However, it has the same discharge time which means its density is higher than LiIon and thus longer life.

A video light has to light a scene properly without hotspots or overpowering the subjects. Tungsten/Halogens are easier to regulate power so you can turn down the power when you are closer to a subject. Some LED and HIDs like the L&M and Amphibicos have multi-power/wattage settings that serve the same purpose.Basically, in daylight, the more powerful light with an even beam, the better. On night dives, a little less light will mean the subjects will less likely swim off. Night shooting also shows hotspotting much more than day shoots. A nice even beam is important.

Color Filters

Having lights in daylight means your illuminated subjects will have correct color renditioning but your background will be more green/blue due to the differences in light. Using filters to correct the light and white balancing can prevent this problem. L&M's Color Management System was designed for this purpose.Changing the color temp of the light using color filters will rob some light, from 1 to 1/3 stop depending on the shift. For example, I use to shift my halogens from 3200K to 4300K using a blue filter (approx -79 mired shift). I lose a stop of light doing that, but with halogen I just change the bulb from 100 to 150 or 200W and more than compensate. The resulting WB is bluer water and proper foreground.HID and LED hover around 6000-6500k so a shift down to 4300-4600 is about a +78 mired shift. Please note 4300-4600K is merely a preference on mine without a red filter for the video. The point is that filters on lights can complement the filter on camera, the ambient light etc for better color accuracy. It is also important to remember that the water between the lights and subject is also absorbing and changing the color temperature. So anything say 3ft(1m) away will appear slightly less red/orange because of the absorption change.Hope this info helps and please feel free to comment.

Drew
Moderator
"Journalism is what someone else does not want printed, everything else is public relations."

"I was born not knowing, and have only had a little time to change that here and there.

i bought the amphibico EVO HD PRO. have only used it a few times. There is a problem with the ULCS connection to the housing the Slot T section keeps sliding of and had already one arm fall off on a dive 30m swim to the bottom to retrieve light (was not impressed). I have designed new connection piece and getting this made. So eagily waiting for another dive.

What software do you use. i am trialing premier however unsure of how to properly balance the colours. Do you use a special program ?

This will need to be updated, as it is incorrect. There are many LED manufacturers who produce hi-performance LED's with a 90+ CRI. The L&M Sunray 2000 (and probably the 1000) are supposed to be in this higher range. L&M are putting together all the specs to publish soon. The cheap LED flashlights with the bluish tint are in that lower CRI range, but not the hi-performance LED's. Plenty of LED info available via Google.Dan

For the traveller and solo diver, travel weight, dive weight, and bouyancy are more important than battery size. Because of that, the fact that HID lamps require ballasts must be weighed against their potentially better efficiency. What really matters is how much light you can carry within your dive restrictions/burn times and whether you can afford to recharge or replace batteries between dives on your total travel weight budget. Depending on wattage, those ballasts can substantially effect the appeal of HID in a negative way. LED is more appealing in that way since it offers durability and high efficiency without the warm-up and ballast issues of HID. I also feel more comfortable in the water without the 40KV electrocution hazard running to my lightheads.

... the fact that HID lamps require ballasts must be weighed against their potentially better efficiency... I also feel more comfortable in the water without the 40KV electrocution hazard running to my lightheads

CraigHID with ballast is still more efficient than halogen and obviously less than LED. However, with the newer battery packs containing Lithium, they are possible fire hazards... depending on who you ask (DOT seems to think yes). Would you like to have 2 lithium packs hooked up to your backplate when it leaks inside and Hydrogen gas is produced? Of course the risks are miniscule but they do exist.

Drew
Moderator
"Journalism is what someone else does not want printed, everything else is public relations."

"I was born not knowing, and have only had a little time to change that here and there.

There are halogen bulbs with efficiencies in excess of 30 lumens/watt. HIDs are generally more efficient than this, but I've seen ratings less than 40 lumens/watt with them. Ballast efficiency for HID lamps is good but it is not 100%. The best halogens have efficiencies that match the worst HID surprisingly. I blame the manufacturers for that since there are HMI lamps at around 70 lumens/watt I believe.

Nevertheless, I'm not speaking of efficiency here, I'm speaking of lumen-minutes per pound. The fact is that we can only dive with so much weight and can only travel with so much as well. A large HID lamp may require a 3 pound ballast, and that's 3 pounds that could go into extra battery to compensate for the lesser efficiency of the halogen bulb.

There's also the matter of how you plan to recharge. Extra batteries add travel weight especially with halogen systems, but high power quick chargers themselves can be large and heavy. It's a complicated issue. Add to that the warmup time and lack of hot restrike in some HIDs and you further complicate the recharging issue. Then there's the issue of variable power which halogen handles pretty easily but HID does not.

Of course, LED threatens to change all this. It's the best of halogen and HID combined assuming the CRI is made good enough.

I would rather not dive with a high power lithium pack underwater. I've flooded a 300+ Wh NiMH pack attached to my backplate and it nearly blew the end plugs off. A lithium version would likely have exploded. When I redesigned my packs, I insisted on threaded end plugs and no switches on the packs themselves. Even though Lithium has an advantage over NiMH in energy density, you have to look at the complete package. Because lithium is so volatile, lithium cells are typically not big. That means that there's a lot of weight overhead in the extra metal packaging that is used. When I did my custom packs, I found no lithium solution that offered an advantage over the best NiMH ones. A full custom pack would be different, of course. Lithium packs also require much more complex chargers and that translates into greater costs and higher travel weight. I'm fine with lithium packs in cameras but I'd prefer them not in my lights and strobes. Just my opinion.

After using many lighting systems over the years
I have been disappointed to the maximum
Some good lights get discontinued for one reason or another
Some systems have too many connections, and that
leads to problems.
Or they are bulky and awkward to attach like the Darkbuster
With some, you have to be a time-keeper relative to HID burn and re-ignite times
which I call "bulb stressing"

Finally, I have found the answer
The Swiss made (by Keldan) Luna-8 WA-V
and while it didn't come cheap
peace of mind is a good thing
especially when you are half way around the world

I just finished some 75 dives with a pair of the Luna-8
They look like a flashlight, and easily connect to Ultra Light arms
I made about 3 dives a day, and the lights never, ever stopped "lighting"
I charged them only overnight.
(Burn times are rated 130-180 minutes low/high, with 5 power settings)

There a some great features
Works both in and out of water
Magnetic switch, very easy to use, 5 power settings!
"smallish" so you can get into tight spaces.
Beam angle of 20 degrees, (distant shots) & 60 degrees with diffuser gives a soft light, w/o hot spots
Not bulky
A battery protection circuit protects the battery from overload, overcharging, and deep discharge
Just a 10-second start-up and cool down interval.

Nice Swiss workmanship to handle.
Very satisfied
see www.keldanlights.com

Updated for LED specs and color filters. (Sorry it took so long but I've had a lot on my plate. )It seems manufacturers (LMI included) are using the 80 CRI LED diodes vs the more expensive 90 CRI variety as suggested by VideoDan. Those 90CRI LED diodes exist but until they are used by manufacturers, it does not warrant being mentioned. This primer will only mention present shipping models and the technologies used. Does 10 CRI pts matter? That's for you to decide. To some (myself included), it's important for correct color. To others, it's not a big deal.

This will need to be updated, as it is incorrect. There are many LED manufacturers who produce hi-performance LED's with a 90+ CRI. The L&M Sunray 2000 (and probably the 1000) are supposed to be in this higher range. L&M are putting together all the specs to publish soon. The cheap LED flashlights with the bluish tint are in that lower CRI range, but not the hi-performance LED's. Plenty of LED info available via Google.Dan

Drew
Moderator
"Journalism is what someone else does not want printed, everything else is public relations."

"I was born not knowing, and have only had a little time to change that here and there.

I would rather not dive with a high power lithium pack underwater. I've flooded a 300+ Wh NiMH pack attached to my backplate and it nearly blew the end plugs off. A lithium version would likely have exploded. When I redesigned my packs, I insisted on threaded end plugs and no switches on the packs themselves. Even though Lithium has an advantage over NiMH in energy density, you have to look at the complete package. Because lithium is so volatile, lithium cells are typically not big. That means that there's a lot of weight overhead in the extra metal packaging that is used. When I did my custom packs, I found no lithium solution that offered an advantage over the best NiMH ones. A full custom pack would be different, of course. Lithium packs also require much more complex chargers and that translates into greater costs and higher travel weight. I'm fine with lithium packs in cameras but I'd prefer them not in my lights and strobes. Just my opinion.

Interesting regarding Li-ion.

From what research I have done, Li-ion should react no more violently than NiMh if exposed to salt water if done right.Also, depending on your battery packs I guess, the Li-ion batteries that I am using (from Salvo) are actually much more reliably charged than Nimh (partly because due to the shape of the canister) and hold their charge better

Also, the chargers and batteries do seem "smarter"

i am getting a 50% power density bonus currently with li-ion over NiMh (15Ah in the same space I would get 10Ah) and if the canister was designed a tad more cunningly, I might get 75% advantage.

For me, Li-ion is the only way to go for my video lighting even though it is a bit more expensive.

From what research I have done, Li-ion should react no more violently than NiMh if exposed to salt water if done right.

What does doing it right involve?

Also, depending on your battery packs I guess, the Li-ion batteries that I am using (from Salvo) are actually much more reliably charged than Nimh (partly because due to the shape of the canister) and hold their charge better

Also, the chargers and batteries do seem "smarter"

LiIon is harder to charge and (generally) requires the extra smarts. This isn't a problem for a commercial product but it is a consideration for a DIY project. LiIon chargers need to be matched to their batteries, NiMH don't.

i am getting a 50% power density bonus currently with li-ion over NiMh (15Ah in the same space I would get 10Ah) and if the canister was designed a tad more cunningly, I might get 75% advantage.

The key measure isn't energy per unit volume, it's energy per unit weight. Weight determines travel-ability and dive-ability. LiIon, done right to insure safety, requires a lot more metal packaging to prevent a catastrophic event. The battery chemistry offers a density advantage but it gives it back in packaging weight. Many years ago there were no LiIon off-the-shelf cells that had better energy per pg than the best NiMH. That may have changed but I haven't noticed the proliferation of large LiIon cells recently.

When I did my custom batteries a while back I still worked at Dell and was good friends with the battery expert there. He offered to help be build custom LiIon packs and to connect me with suppliers. He also told be that there would be a serious explosion risk at the sizes I wanted. If that's not true, I'd like to see any data that says LiIon doesn't suffer those concerns. LiIon packs in notebook computer sizes have exploded and killed people. My video light batteries were considerably larger.

limeyx, is your solution custom or a commercial product? Details? You said 15Ah instead of 10Ah. At what voltage and what size?

Here is the rig I did quite a few years ago:Each battery pack was 21 cells of NiMH at 4.5Ah and weighed 3.5 pounds, producing a 25V pack that drove 24V bulbs from 50-400 watts. At high currents I claimed the packs were 100Wh to comply with airline regulations Also shown are the single pack and double pack cannisters that allowed me to dive with up to 450 Wh on my backplate at about 12 pounds of negative bouyancy. The batteries were rated to 3C discharge and would allow up to 1200W for about 15 minutes. The most I ever used was 800W and I got over 25 minutes out of them.

Well, I am far from an expert on Li-ion or NiMh
I use a commercial product -- Salvo Li-ion batteries (15Ah) and used to use a 10Ah Li-ion battery and 9.6Ah Nimh from Halcyon.

The Halcyon products (and the old Salvo Nimh) were harder to maintain than the lithium due to pack designs where the charger (I believe) charged just the first 1/2 or 1/3 of the pack and the charge "trickled" into the other packs sometimes resulting in a 1/2 or 1/3 charge.

For me, charging Li-ion is much more reliable but I am using commercial packs & chargers.

I can get 15Ah Li-ion in a canister that can only get 9.6Ah Li-ion which means 80 mins BT not 45 on my dual 50W HIDs which is a clear win for me even if the pack is a little heavier.

For home-made, I have no knowledge and NiMh may indeed be easier to work with. Not really my area --- I prefer to take video than tinker with batteries

On the risk of explosion I am going by what Salvo says so not a real world "I tried it and didn't blow my arm off (yet)"

"Yea, it is a slow day in the diving community. We had put up the page to offset other misinformation people without a clue were saying about Li-ion batteries, like say they explode if flooded in saltwater which is not true. It served its purpose and was removed. The removal had nothing to do with the customer who had a problem with one of our products. In the end, it turned out to be the controller in the pack that melted down. The customer asked we replace the light with the same one and he was happy."